The present invention relates to the thermal insulation of molten metal.
In many cases in the foundry and steel making industries it is desired to minimize the loss of heat from bodies of molten metal--for example in ladles and tundishes, or in the heads of solidifying ingots, or in the risers of castings.
It is customary to line the sides of ingot moulds, casting risers, ladles and tundishes with a layer of heat insulating material. However, the maximum insulation attainable by this method is often considered insufficient, and methods have therefore been proposed to minimize the heat loss from the horizontal molten metal surface.
Such methods include the provision of a moulded insulating cover (for example of plaster, clay, fire-brick) or of a layer of powdered heat insulating material (for example rice husks). In addition, it may be desirable positively to supply heat to the molten metal and the use of an exothermic composition has been proposed and employed. A further known procedure is to place on the molten metal surface a mixture of loose powdered exothermic material and loose powdered heat insulating material contained in a cardboard or like container to ease handling. However, these procedures have proved to be unsatisfactory because of the high inclusion levels of these loose powdered materials in the surface of the solidified metals. Further, as can be appreciated the loose powdered materials, because they must be shipped and stored in containers which may spill or leak, are often difficult to handle and often lead to an unevenness in the level of application with a consequent unevenness in the heat insulating properties of the insulative coating.
It is, therefore, an object of the present invention to provide a heat insulating material which when applied to the exposed surfaces of molten metal affords covering for the surface of the molten metal and a low inclusion level of the insulation material in the solidified molten metal.
It is also an object of the invention to provide a heat insulating material for application to the exposed surfaces of molten metal which is self-supporting and, therefore, easy to handle, ship, store and apply.